(1) Field of the Invention
The present invention relates to an apparatus for ejecting, underwater, an object from a naval vessel and more particularly launching a tethered object from a submerged submarine.
In typical submarine underwater communication systems wherein the seawater is used as the medium through which communication signals are transmitted, it is desirable to position a communications transmitting package at some distance from the vessel. Generally the communication package utilizes a tether line comprising electric or fiber optic transmission means therein thereby forming a hard communication link between the communication package and the vessel. Many times the communication package is towed at some distance behind the vessel. In these instances the tether line not only provides a communications link with the vessel but also acts as a tow cable and must necessarily be prevented from becoming entangled in the vessel's propellers or other external appendages during normal maneuvers. This is particularly troublesome in submarine operations.
Further, as is easily understood, particularly for submarine type vessels, it is most desirable that the launch of such communication devices be accomplished without creating significant acoustic pressure impulses.
(2) Description of the Prior Art
Heretofore, in submarine operations, it has been known to mount a non-reloadable, one shot type launcher mechanism outside of the ship's pressure hull and far enough aft to allow clearance of the ship's structure by the ejected instrument package. This approach is undesirable as it requires an added appendage to the otherwise carefully configured hydrodynamic shape of the submarine and will most likely introduce hydrodynamic turbulence during normal cruising of the vessel thereby creating an acoustic pressure disturbance. Further, such a one shot system would necessarily be reloadable only when operating above the surface or when in port; therefore, multiple launchers would be necessary compounding the hydrodynamic noise problem. Such one shot systems are obviously impractical in view of the long duration underwater voyages of which our nuclear submarines are capable.
Further such external appendages would necessarily incorporate short launch tubes requiring rapid acceleration of the ejected instrument package so as to obtain the escape velocities necessary to propel the instrument package the necessary distance from the ejecting vessel.